Vous is the formal 'you' form. Using it
shows respect and social distance. It should always be used when addressing
strangers except for in certain environments like school where students normally
use tu with each other. Permission should be asked before using tu,
but you normally shouldn't ask if someone is significantly older than you. It
should always be employed when addressing people of authority like your teachers
or the police.

Normally, the final consonant of a word ending in s isn't pronounced. when followed by a vowel ending word
or a word that begins with silent h, this final consonantis pronounced. This is called liaison.